Japanese Patent Laid-Open Publication No. 09-148325 discloses a technology of achieving a silicon oxynitride film excellent in uniformity of in-plane film thickness and in electrical characteristics. Specifically, a semiconductor wafer is heated to the temperature of about 1100° C. in an atmosphere containing oxygen gas to form a silicon oxide film having a predetermined film thickness on the semiconductor wafer. Then, with NH3 gas introduced onto the semiconductor wafer heated to about 1000° C., the silicon oxide film is nitrided to form a silicon oxynitride film. Then, with the degree of vacuum kept under 25 Torr, the semiconductor wafer is kept at about 1100° C. and for 30 seconds for dehydrogenation of the silicon oxynitride film.
Japanese Patent Laid-Open Publication No. 06-209009 discloses a method of fabricating a semiconductor device including the steps of: nitriding a surface of a semiconductor substrate; forming a silicon oxide film on the nitrided semiconductor substrate; and forming a silicon oxynitride film by increasing the density of the silicon oxide film.
Japanese Patent Laid-Open Publication No. 06-291330 discloses a non-volatile semiconductor memory device. Specifically, the non-volatile semiconductor memory device has, as a first insulating film, a charge-injectable tunnel insulating film on a surface of a semiconductor substrate, the tunnel insulating film being formed of a tunnel silicon oxynitride film and a tunnel silicon oxide film provided on the tunnel silicon oxynitride film. The memory device further includes a gate insulating film having stacked thereon a silicon nitride film as a second insulating film and a silicon oxide film as a third insulating film, and also includes a gate electrode provided on this gate insulating film.